Clamp for use with electroplating apparatus and method of using the same

ABSTRACT

A clamp for use in an electrolytic plating bath is disclosed. The clamp comprises two levers  at least two opposing levers, at least one lever being pivotally attached to each other at  a fulcrum wherein the clamp, when floating on top of a liquid, is in an open position but when submerged is caused, by virtue of its buoyancy, to move to a closed position. Each lever comprises a first part integrally attached to a second part. The first part and the second part are situated on opposite sides of the fulcrum from each other such that rotational movement about the fulcrum between the open position and the closed position causes the second parts of each lever to move from an upper position to a lower position. In operation, at least one substrate is supported in a substantially vertical plane for submersion into an electrolyte bath. The substrate is positioned over the electrolyte bath and then is submersed into it. The clamp clamps the substrate at its lower edge as the substrate enters the electrolyte bath.

This invention relates to a clamp.

In particular this invention relates to a buoyancy activated clamp.

In addition this invention relates to a cathode shield, electroplatingapparatus and method using a clamping means.

Known clamps are not very sutiable suitable for use in automatedprocesses.

In U.S. Pat. No. 4,879,007 (to the same assignee, and incorporated inthis specification by reference) a means for increasing the efficiencyand speed of automated electroplating is described. Substrates to beelectroplated are automatically clamped at the top and brought in to besuspended over an electrolyte bath. The substrates are then lowered intothe bath, at which time their lower edges contact a cathode shielddevice floating on the top of the bath. The weight of the substrates andthe pressure bearing down upon them is sufficient to overcome thebuoyancy of the shield and to move it down into the electrolyte bath.Flexible substrates, however, even if they are able to bear down enoughon the cathode shield to push it into the bath, tend to warp and wobble,creating an uneven pattern of electroplating on the substrate. Thisproblem is usually over come by placing around the perimeter of flexiblesubstrates, a rigid frame. This solution has a number of drawbacks:firstly, the substrates usually must be loaded by hand; secondly, theframe gets coated with metal as well, which metal must then be scrapedoff; and thirdly, in view of the above drawbacks, the electroplatingprocess is rather slow.

The object of the present invention is to overcome the abovedisadvantages or difficulties or at least to provide public with auseful choice.

Accordingly, in a first embodiment this invention consists in a clampcomprising two levers pivotally attached to each other at a fulcrumwherein the clamp, when floating on top of a liquid, is in a firstposition but when submerged, by virtue of its buoyancy is caused to moveto a second position.

In a second embodiment, the present invention consists in a method forthe electrolytic deposition of a coating of metal on an electroplatablesubstrate as cathode in an electrolyte bath equipped with anode whereinthe substrate is supported in a substantially vertical plane and isautomatically clamped at its lower edge as it enters the electrolytebath.

In a third embodiment, the present invention consists in a cathodeshielding device for use in an electrolytic plating bath, said devicecomprising: an elongated trough adapted to be inserted in said bath;said trough being provided with a plurality of clamps comprising twolevers pivotally attached to each other at a fulcrum wherein the clamp,when floating on top of a liquid, is in a first position but whensubmerged, by virtue of its buoyancy is caused to move to a secondposition; said clamps being aligned substantially in parallel verticalplanes transverse to the longitudinal axis of said trough, for securingone or more electroplatable substrates in a substantially vertical planewith the lower edge of each of said substrates located below the planein which lies the upper edges of said trough; and said trough having aplurality of perforations in the upper region of the sides thereof.

In a fourth embodiment, the present invention consists in an apparatusfor electrolytic deposition of metal on a substrate comprising acontainer for electrolyte; a cathode bus bar; and a clamping means,wherein an electroplatable substrate is attachable at an upper edge tothe cathode bus bar and the clamping means clamps lower edge of anysubstrate attached to the cathode bus bar as the substrate enters thecontainer.

Preferred embodiments of the invention will now be described withreference to the drawings in which:

FIG. 1 is a schematic side view of the clamp of the present invention ina closed position.

FIG. 2 is a schematic side view of the clamp of the present invention inan open position.

FIG. 3 shows in perspective view, partially cutaway, a cathode shield ofthe present invention.

FIG. 4 is a cross-sectional view of a cathode shield incorporating theclamp and with an electroplatable substrate in place.

FIG. 5 is a perspective view partially cutaway showing the cathodeshield of FIG. 3 mounted in a plating bath.

FIG. 6 is a schematic, cross-sectional view of a cathode shield of theinvention installed in an unloaded condition in a plating bath.

FIG. 7 is a perspective view of the cathode shield of the inventionmounted in a frame with electroplatable substrates loaded.

FIG. 8 is a perspective view of a cathode shield of the presentinvention showing one end of the shield in detail.

A preferred embodiment of the clamp of this invention is illustrated inFIGS. 1 and 2. As clamps operable by buoyancy have not previously beenknown it will be understood that such a clamp could take on a number ofconfigurations and the configuration shown in FIGS. 1 and 2 is purely byway of example. In FIG. 2, the clamp is shown as being made up of twolevers 52, 54 which are pivotally attached to each other at a fulcrum56. For some applications it may be desirable for the levers 52, 54, tobe formed in two parts 58, 62 and 60, 64 on either side of the fulcrum,the first parts 58, 62 being buoyant and performing the clampingfunction and the second parts 60 and 64 performing an auxiliaryfunction. In the open position shown in FIG. 2, gripping members 66 arespaced apart from each other. The second parts 60, 64 conveniently form,in the open position, a pathway to guide an object to be clamped intothe space between the gripping members 66. The second parts of 60, 64therefore act as guide members. The clamp is buoyant so it will float onthe top of a liquid in the position shown in FIG. 2.

When the clamp is forced downwards into the liquid the tendency for thebuoyant first parts 58, 62 of the levers 52, 54 is to move in an upwarddirection until they reach the limit of upward movement which is definedby the gripping members being pressed together on either side of theobject to be gripped (or pressed against each other if no object ispresent).

Upon return to the surface of the liquid the clamp will again assume anopen position.

The clamp may of course be configured so that it clamps when floatingand releases when submerged. This may most conveniently be achieved bythe gripping members being located on the second parts 60, 64 of thelevers 52, 54. Alternatively, the gripping members could be located onthe under side of the first parts 58, 62 of the levers 52, 54. Asmentioned above, the clamp's configuration is not limited to the exampleshown in FIGS. 1 and 2 but can be configured to suit the overallfunction it performs in whatever apparatus it may be utilised in.

One particularly appropriate use of the clamp of the invention is,however, as part of a cathode shield in an electroplating bath where theclamps hold electroplatable substrates in place and is advantageous inthat very flexible substrates can be securely retained in theelectroplating bath.

FIG. 3 shows a perspective view, with one side partially cutaway to showdetails of the interior, of a shielding device shown overall as 4according to a preferred embodiment of the invention. The shield 4comprises an elongated trough 5 bounded by sidewalls 6 and 8, and strutengaging members 10 and 12 and a floor 14. It will be understood thatthe strut engaging members 10, 12 need not be positioned at the ends ofthe trough but are most suitably so placed. The floor 14 is raised abovethe level of the lower edges of the sidewalls 6 and 8 thus leaving anopen compartment 16 beneath the floor 14 of the shield. Disposed withinthe shield are a plurality of clamps 18 which serve to secure thesubstrates which are to be electroplated. The lower edge of a substrate24 is received as shown in cross-section in FIG. 3 4. As shown in FIG.3, the gripping members are below the level of the upper edge of walls 6and 8 by a distance “x”. In general, the distance “x” is within therange of about 2 cms to about 10 cms and preferably in the range ofabout 3 cms to about 6 cms although values of “x” higher than or lowerthan this can be employed if desired. Preferably, however, the distance“x” is not less than about 1.5 cms.

The clamps 18 all pivot about a rod 70 which is secured at either end bythe strut engaging members 10, 12 or in some other way so that theclamps may pivot freely. For convenience the entire of side walls 6, 8need not be attached to the levers 52, 54, but can be formed in twoparts as shown in FIG. 8. The lower part of the side walls 6, 8 willtherefore be remain substantially vertical at all times, whereas as theupper part will be at an angle to the lower part when the trough isfloating on top of the bath.

Referring again to FIG. 3, each of the sidewalls 6 and 8 has a pluralityof perforations 26 in the upper regions thereof to permit electrolyte inthe bath to flow therethrough into and out of the trough 5. The numberand arrangement of these perforations is not critical although it ispreferred that no perforations are present in either sidewall below thelevel the gripping members (see FIG. 4).

In the loaded condition the device 4 is immersed in the bath to thedepth required by exerting a downwards pressure on the trough.

Referring to FIG. 8, a downwards pressure is conveniently exerted on thetrough 5 by struts 72 attached to the cathode bus bar 38 (see FIG. 7).The strut 72 has a strut end 74 which engages with a strut engagingmember 10. The strut end 74 and strut engaging member 10 are shown ashaving corresponding V-shapes, but many have other corresponding shapes,such as a tooth arrangement. The strut 74 and the strut engagementmember 10 must, however, engage in such a manner so that lateralmovement in the strut 72 creates a corresponding lateral movement in thetrough 5 and does not cause the strut 72 to became disengaged from thestrut engaging member 10. To aid such an engagement, the strut end 74 ispreferably provided with a retainer 76 to retain the strut 72 inposition relative to the strut engaging member 10. The strut engagingmember 10 could be formed by one of the clamps 18 in the trough 5 asillustrated in FIG. 7.

The strut could alternatively extend upwards from the trough and engagewith a strut engaging member on the cathode bus bar 38. Or, both thetrough and the bus bar could be provided with struts which engage witheach other.

Thus, in operating an electroplating process in accordance with theinvention, the cathode bus bar 38, with the substrates 24 attached bymeans of clamp 39 and connecting harness 40 moves into position over theelectrolyte bath 30 and the trough 5. The cathode bus bar 38 then lowersthe substrates down towards the trough and the guide members (secondparts) 60, 64, guide the lower edge of the substrates into the spacebetween the gripping members 66. At the same time the strut 74 engagesthe strut engaging member 10. The bus bar continues to move downwardlyand pushes the trough, via the strut 74 into the electrolyte. As theclamps 18 become submerged the gripping members 66 close on either sideof the substrates 24 to hold them in a substantially vertical plane.When electroplating is completed, the cathode bus bar 38 and attachedsubstrates move upwardly and the trough, by virtue of its buoyancy, alsomoves upwardly. When the trough reaches the top of the electrolytesolution, the clamps 18 open and the gripping members move apart torelease the substrates 24. The substrates are then lifted clear of theelectrolyte bath and moved away by the cathode bus bar.

The struts 74 are conveniently placed one at each end of the trough 5,however more struts 74 could be provided if desired. If only one strut74 is utilised the corresponding strut engagement member 10 would needto be exactly centrally placed.

A guide (not shown) may be situated on each side of the bath 30 toprevent gross lateral movement of the trough, but such a guide wouldobviously allow for the reciprocating motion which is part of theelectroplating process as described below.

A feature of the clamp illustrated in FIGS. 1 and 2, is that the guidemembers 60, 64 which form a steep sided V-shape when the clamp is in theopen position, form a very wide V-shape when the clamp is in the closedposition.

If the guide members were to retain a steep V-shape after immersion inthe electrolyte, they might hinder electroplating by creating a “shadow”on the substrate. However, if the guide members were to retain a wideV-shape, which would not interfere with the electroplating process, theywould not so efficiently guide moving substrates into position.

The components of trough 5 and clamps 18 are advantageously prepared byinjection molding or like means as a single unitary whole or in pieceswhich are assembled by melt sealing or like means from plastic materialsuch as polyethylene, polypropylene and the like which impart sufficientbuoyancy to the device 4 to enable it to float in the electrolyte 27 ofthe plating bath as shown substantially in cross-section in FIG. 6. Thecomponents of trough 5 and plates 18 may also be fabricated from plasticmaterial such as polyvinyl chloride which is of a density such thatdevice 4 does not have sufficient buoyancy to float. In this event,material such as a block or blocks of polystyrene foam or polyurethanefoam is attached to device 4, advantageously by placement of theappropriate amount of such foam block in compartment 16 (see FIGS. 3,and 4), to impart sufficient buoyancy to the device 4 to enable it tofloat. The appropriate amount of auxiliary buoyant material required canbe determined readily by a process of trail trial and error.

FIG. 5 shows in partial cutaway a perspective view illustrating anothermanner in which the device 4 is mounted in a plating bath 30 inaccordance with the invention. In this embodiment the strut 72 of device4 is mounted in the second parts 60, 64 of a clamp 18. The struts 72 areattached to a cathode bus bar 38 (FIG. 7) to which limited reciprocatingmotion can be imparted in the direction indicated by the arrows byappropriate reciprocating drive means (not shown).

The reciprocating motion imparted to device 4 in the above mannerencourages circulation of electrolyte around the substrates suspended inthe plating bath. This motion takes place in the gap between twin anodes36 and 36′ shown in cross-section in FIG. 6 which anodes each extendsubstantially across the width of bath 30 in a direction parallel to thelongitudinal axis of device (4). These anodes 36 and 36′ are not shownin FIG. 5 in order not to obscure the details of the manner in which thedevice 4 is mounted in bath 30.

The buoyancy activated clamp, the cathode shielding device using a clampand using the clamp of the invention and the methods of utilizing saiddevice in an electroplating bath have been described above by referenceto various specific embodiments shown in the drawings appended hereto.The scope of the invention is not limited to these particularembodiments, and various modifications which will be readily apparent tothose skilled in the art can be made to said illustrative embodimentswithout departing from the scope thereof.

The invention provides an improved cathode shield device for use in anelectroplating bath and process. The device is very easy to load,relatively simple in construction and contributes significantly to theeconomics of an electroplating operation by reason of the time and laborwhich is saved by its utilization. Furthermore, the device isparticularly useful with very light and flexible substrates which arenot sufficiently securely retained during the electroplating process inpreviously disclosed cathode shields. In addition the buoyancy activatedclamp is a significant contribution to the art in that no externalclamping means is required. This makes the buoyancy activated clampparticularly useful in automated processes.

I claim:
 1. A clamp for use in an electrolytic plating bath, the clampcomprising: two levers at least two opposing levers, at least one leverbeing pivotally attached to each other at a fulcrum and movable betweenan open and a closed position, each lever comprising a first part and asecond part, the first part being integrally attached to the secondpart, the first part comprising a guide member for guiding an object tobe clamped, each part being situated on opposite sides of the fulcrumfrom each other such that rotational movement about the fulcrum betweenthe open position and the closed position causes the second parts ofeach lever to move from an upper position to a lower position when theclamp is submersed into a liquid, the clamp further comprising at leasttwo gripping members, at least one griping member being situated on eachlever, wherein when the levers are in a closed position the grippingmembers are adjacent to each other and are on either side of the objectto be clamped, and wherein when the levers are in an open position, thegripping members are spaced apart from each other , said clamp beingoperable between the open and closed positions by virtue of itsbuoyancy.
 2. The clamp for use in an electrolytic plating bath of claim1, wherein when the levers are in the open position, the guide membersof each lever guide an object to be clamped into the space between thegripping members.
 3. The clamp for use in an electrolytic plating bathof claim 1 18, wherein the guide members extend upwardly and outwardlyin substantially a v-shape from the space between the gripping memberswhen the levers are in the open position.
 4. The clamp for use in anelectrolytic plating bath of claim 3, wherein the two guide members forman angle therebetween, wherein the angle between the guide members issmaller when the levers are in the open position than when the leversare in the closed position.
 5. A method for electrolytic deposition of acoating of metal on an electroplatable substrate, the substrate having alower edge, the method comprising the following steps: supporting atleast one substrate in a substantially vertical plane; for submersioninto an electrolyte bath; positioning the substrate over the electrolytebath; submersing the substrate into the electrolyte bath; and clampingthe substrate at its lower edge as the substrate enters the electrolytebath, wherein the step of clamping the substrate comprises the step ofmoving a clamp between an open position and a closed position as thesubstrate is submersed into the electrolyte bath, the clamp comprisingat least two levers pivotally attached to each other at a fulcrum, andat least one gripping member located on each lever for gripping thesubstrate, wherein the clamp, when floating on top of the electrolytebath is in an open position, but when submersed into the electrolytebath is caused, by virtue of its buoyancy, to move to a closed position,such that in the open position the gripping members are spaced apartfrom each other, and such that in the closed position, the grippingmembers are adjacent to each other and on either side on the substrateso as to grip the substrate with the gripping members.
 6. A cathodeshielding device for use in an electrolyte plating bath, said devicecomprising: an elongated trough in a frame, the trough capable ofhousing at least one electroplatable substrate in a substantiallyvertical plane; and aat least one clamp disposed in the trough forclamping the electroplatable substrate, thesaid clamp comprising atleast two opposing levers, at least one lever being pivotally attachedto each other at a fulcrum and movable between an open and a closedposition, each lever comprising a first part and a second part, thefirst part being integrally attached to the second part, the first partcomprising a guide member for guiding an object to be clamped, each partbeing situated on opposite sides of the fulcrum from each other suchthat rotational movement about the fulcrum between the open position andthe closed position causes the second parts of each lever to move froman upper position to a lower position when the clamp is submersed intothe electrolyte plating bath.
 7. The cathode shielding device for use inan electrolyte plating bath of claim 6, wherein the clamp furthercomprises at least two gripping members, at least one griping grippingmember being situated on each lever at least two levers, wherein whenthe levers are in a closed position the gripping members are adjacent toeach other and are on either side of the object to be clamped, andwherein when the levers are in an open position, the gripping membersare spaced apart from each other.
 8. The cathode shielding device foruse in an electrolyte plating bath of claim 7, wherein the levers are inthe open position, the guide members of each lever guide an object to beclamped into the space between the gripping members.
 9. The cathodeshielding device for use in an electrolyte plating bath of claim 8,wherein the guide members extend upwardly and outwardly in substantiallya v-shape from the space between the gripping members when the leversare in the open position.
 10. The cathode shielding device for use in anelectrolyte plating bath of claim 9, wherein the two guide members forman angle therebetween, wherein the angle between the guide members issmaller when the levers are in the open position than when the leversare in the closed position.
 11. The cathode shielding device for use inan electrolyte plating bath of claim 10, wherein the substrate comprisesa printed circuit board.
 12. An apparatus for electrolytic deposition ofmetal on a substrate, said apparatus comprising a container forcontaining electrolytic fluid; a cathode and an anode mounted in thecontainer, and a cathode shielding device, the cathode shielding devicecomprising: an elongated trough, the trough comprising an upper edge ina plane, the trough capable of housing an electroplatable substrate in asubstantially vertical plane, the substrate having a lower edge in aplane, the lower edge of the substrate located in the same plane inwhich lies the upper edge of the trough; and at least one clamp disposedinside in the trough for clamping the electroplatable substrate, theclamp comprising two levers at least two opposing levers, at least onelever being pivotally attached to each other at a fulcrum and movablebetween an open and a closed position, wherein each lever comprises afirst part and a second part, the first part being integrally attachedto the second part, the first part comprising a guide member for guidingan object to be clamped, each part being situated on opposite sides ofthe fulcrum from each other such that rotational movement about thefulcrum between the open position and the closed position causes thesecond parts of each lever to move from an upper position to a lowerposition when the clamp is submersed into a liquid.
 13. The cathodeshielding device for use in an electrolyte plating bath of claim 12,wherein the clamp further comprises at least two gripping members, atleast one griping gripping member being situated on each of lever atleast two levers, wherein when the levers are in a closed position thegripping members are adjacent to each other and are on either side ofthe object to be clamped, and wherein when the levers are in an openposition, the gripping members are spaced apart from each other.
 14. Thecathode shielding device for use in an electrolyte plating bath of claim13, wherein when the levers are in the open position, the guide membersof each lever guide an object to be clamped into the space between thegripping members.
 15. The cathode shielding device for use in anelectrolyte plating bath of claim 14, wherein the guide members extendupwardly and outwardly in substantially a v-shape from the space betweenthe gripping members when the levers are in the open position.
 16. Thecathode shielding device for use in an electrolyte plating bath of claim15, wherein the two guide members form an angle therebetween, whereinthe angle between the guide members is smaller when the levers are inthe open position than when the levers are in the closed position. 17.The cathode shielding device for use in an electrolyte plating bath ofclaim 12, wherein the substrate comprises a printed circuit board. 18.The clamp for use in an electrolytic bath according to claim 1 furthercomprising at least two gripping members, at least one gripping memberbeing situated on at least two levers, wherein when the levers are in aclosed position the gripping members are adjacent to each other and areon either side of the object to be clamped, and wherein when the leversare in an open position, the gripping members are spaced apart from eachother.
 19. A clamp for use in an electrolytic plating bath, comprising:at least two opposing gripping members, at least one gripping memberbeing pivotally disposed about a fulcrum so as to be capable of grippingthe substrate and movable between opened and closed positions whereinsaid clamp, when floating on top of the electrolyte bath is in an openposition, but when submersed in the electrolytic bath is caused, byvirtue of its buoyancy, to move to a closed position, such that in theopened position the gripping members are spaced apart from each other,and such that in the closed position, the gripping members are adjacentto each other and on either side of the substrate so as to grip thesubstrate with the gripping members.
 20. The method for electrolytedeposition of a coating of metal on an electroplatable substrateaccording to claim 5 wherein said clamping step further comprises atleast two gripping members, at least one gripping member being situatedon at least two levers for gripping the substrate, wherein when theclamp, when floating on top of the electrolytic bath is in an openedposition, but when submersed into the electrolytic bath is caused, byvirtue of its buoyancy, to move to a closed position, such that in theopened position the gripping members are spaced apart from each other,and such that in the closed position, the gripping members are adjacentto each other and on either side on the substrate so as to grip thesubstrate with the gripping members.
 21. A method for electrolyticdeposition of a coating of metal on an electroplatable substrate, thesubstrate having lower edge, the method comprising the following steps:supporting at least one substrate in a substantially vertical plane overan electrolytic bath; submersing the substrate in the electrolytic bath;and clamping the substrate at its lower edge as the substrate enters theelectrolytic bath; wherein the step of clamping the substrate comprisesmoving a clamp between an opened position and a closed position as thesubstrate is submersed into the electrolytic bath, the clamp comprisingat least two opposing gripping members, at least one gripping memberbeing pivotally disposed about a fulcrum so as to be capable of grippingthe substrate and movable between opened and closed positions whereinsaid clamp, when floating on top of the electrolytic bath is in anopened position, but when submersed in the electrolytic bath is caused,by virtue of its buoyancy, to move to a closed position, such that inthe opened position the gripping members are spaced apart from eachother, and such that in the closed position, the gripping members areadjacent to each other and on either side on the substrate so as to gripthe substrate with the gripping members.
 22. A cathode shielding devicefor use in an electrolytic plating bath, said device comprising: anelongated trough in a frame, the trough capable of housing at least oneelectroplatable substrate in a substantially vertical plane; and atleast one clamp disposed in said trough for clamping the electroplatablesubstrate, said clamp comprising at least two opposing gripping members,at least one gripping members being pivotally disposed about a fulcrumso as to be capable of gripping the substrate and movable between openedand closed positions wherein said clamp, when floating on top of theelectrolytic bath is in an opened position, but when submersed in theelectrolytic bath is caused, by virtue of its buoyancy, to move to aclosed position, such that in the opened position the gripping membersare spaced apart from each other, and such that in the closed position,the gripping members are adjacent to each other and on either side ofthe substrate so as to grip the substrate with the gripping members. 23.An apparatus for electrolytic deposition of metal on a substrate, saidapparatus comprising a container for containing electrolytic fluid; acathode and an anode mounted in the container, and a cathode shieldingdevice, the cathode shielding device comprising: an elongated trough,the trough comprising an upper edge in a plane, the trough capable ofhousing an electroplatable substrate in a substantially vertical plane,the substrate having a lower edge in a plane, the lower edge of thesubstrate located in the same plane in which lies the upper edge of thetrough; and at least one clamp disposed in said trough the clamping theelectroplatable substrate, the clamp comprising at least two opposinggripping members, at least one gripping member being pivotally disposedabout a fulcrum so as to be capable of gripping the substrate andmovable between opened and closed positions wherein said clamp, whenfloating on top of the electrolytic bath is in an opened position, butwhen submersed in the electrolytic bath is caused, by virtue of itsbuoyancy, to move to a closed position, such that in the opened positionthe gripping members are spaced apart from each other, and such that inthe closed position the gripping members are adjacent to each other andon either side of the substrate so as to grip the substrate with thegripping members.